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That's different than those that would click on an advertisement and then proceed all the way through to a purchase hence my original reply.
If you are wanting to know what percentage of people will hit your site, follow your aff. link to the merchant then make a purchase, that is almost impossible to estimate.
It would depend on the product being sold, is it a low-end product, high end product? A lead-capture site? What type of site do you have? Is it a review site? Simply a content site?
There are a ton of factors involved.
[edited by: Philosopher at 8:32 pm (utc) on May 11, 2009]